Abstract: A three-drug injection mixture of alprostadil 12.5 µg/mL,
papaverine hydrochloride 4.5 mg/mL and phentolamine
mesylate 0.125 mg/mL in bacteriostatic 0.9% sodium chloride
injection was evaluated for stability at 23°C, 4°C,
-20°C and -70°C. The injection remained clear and colorless
in all samples throughout the study. Chemical stability
testing was performed using stability-indicating high-performance
liquid chromatographic analysis. Alprostadil was
the least stable of the drug components at room temperature
and under refrigeration. About 8% alprostadil loss occurred
in five days at room temperature; under refrigeration
losses of about 6% and 11% occurred after 1 and
2 months, respectively. Frozen at -20°C and -70°C, less
than 5% loss of any of the drug components occurred in
6 months.

A beyond-use date of 6 months when stored frozen at
-20°C and 1 month when stored refrigerated at 4°C is appropriate
for batches of the injection that have passed
sterility testing. Room temperature exposure should be
limited, and the vial should be returned to refrigeration as
soon as possible.